(1. Geotechnical Engineering Research Institute，Hohai University，Nanjing，Jiangsu 210098，China；2. Key Laboratory for Geomechanics and Embankment Engineering of Ministry of Education，Hohai University，Nanjing，Jiangsu 210098，China；3. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China；4. Lille University of Science and Technology，Lille 59650，France)
Abstract：Investigating the degradation evolution process of rock deformation by mesoscopic experiment is an important means to understand its deformation and failure mechanisms. In this paper，the marble samples are taken from the tunnels of Jinping II hydropower station with an overburden depth of 2 525 m. By mesomechanical test system，axial compression test is carried out to record the whole degradation deformation process of rock. With the image processing technique of scanning electron microscope(SEM)，we quantitatively analyze the initiation，propagation and coalescence processes of microcracks；and the data of microcracks′ area，azimuth angle，length，width and perimeter are obtained. Meanwhile，internal variable thermodynamics theory and frictional kinking crack model are employed to understand the evolution process of microcracks at different stages. Quantitative relationship between nonelastic strain(induced by microcracks) and stress is established and theoretical curve of stress vs. strain is also derived. With the experimental results，validity of the theoretical model is verified，and the failure mechanism of rock samples under axial compression is investigated in terms of experiment and theory.
ROBINA H C，WONG K T，WANG C P. Microcracking and grain size effect in Yuen Long marbles[J]. International Journal of Rock Mechanics and Mining Sciences，1996，33(5)：479-485.
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2013, Vol. 32 
